Determine the nature of dark matter using Milky Way stellar streams

Determine the fundamental nature of dark matter by leveraging constraints from Milky Way stellar streams that have been discovered and characterized with Gaia astrometry and spectroscopy, which provide sensitive probes of the Galactic gravitational field and dark matter substructure.

Background

The review emphasizes that stellar streams—tidal debris from disrupted globular clusters and dwarf galaxies—are exceptionally sensitive tracers of the Milky Way’s gravitational potential, including its dark matter component. Because streams retain coherent dynamical structure over gigayear timescales, their morphology and kinematics encode information about the mass distribution and substructure of the dark halo.

Gaia’s all-sky astrometry and photometry have catalyzed a step change in the number, quality, and characterization of known streams, enabling measurements of orbits, density variations, and perturbations that are predicted to arise from dark-matter subhalos. These measurements position stellar streams as a leading avenue to probe dark matter microphysics and halo structure, thereby addressing the long-standing question of dark matter’s nature.